SIN 2002C3 ICA UPS capacity 25,000 VA, inverter only works when the AC input voltage is low or dead. When the AC input voltage under normal circumstances, ICA UPS will stabilize and filter the input voltage and AC voltage supply a clean and stable ICA UPS output and to charge the batteries. When the AC input voltage is low or not, the inverter will replace it and supply a stable AC voltage over time-a very short time.